If the tracker fails, it is often because the aspect of the tracked pattern has changed significantly between the reference frame (the track start frame) and the current frame.
If the solver has already been launched, you can verify the distance in pixels between a 2D point and the projection of a 3D point on the camera in the 2D View or in the Survey View. You can examine the residuals for all the points and frames. Sort them by frame and check if any points have a high residual value. See Examining the computation quality in the Survey Window.
If so, it is probably because the point has been poorly located by the 2D tracker. If a frame has a high error, viewed in the Frame mode, this may be due to the bad positioning of a 2D computed point within the frame.
By examining the errors on the points in the Points mode, it is possible to find the computed 2D point responsible for the high error. It is then useful to restart the tracker from an intermediate frame (insert an intermediate key), where the tracked position is correct, and the aspect is more similar to the current frame.
You can also check the track path for bumps. If the track path is jagged, it means that either the camera follows a jerky motion, or that the point suddenly drifted during tracking. In this case, you should return at the time the track jumped, and correct it by creating a new key at the appropriate coordinates and resuming tracking.
Another potential cause for the tracker to stop is when the point image motion is so fast that the search area of the tracker becomes smaller than the point displacement between two consecutive frames.
If this is the case enlarge the search area and re-run the tracker from the last correct frame, then reduce the search area to a normal size.
When a point that is being tracked starts to leave the image, MatchMover shows a warning message and the 2D tracker stops. When the quality of the tracking falls below the defined threshold a warning message appears and the tracking stops.
